Methods of making transreflectors

ABSTRACT

The transreflectors may comprise two or more transparent substrates of different indices of refraction bonded together, with a pattern of optical deformities in the mating side of one of the substrates and an inverse pattern of optical deformities in the mating side of an other substrate in mating engagement with each other. The transreflectors are used in a transreflector system or display to transmit more of the light emitted by a backlight or other light source incident on one side of the transreflectors and reflect more of the light incident on the opposite side of the transreflectors.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.10/683,630, filed Oct. 10, 2003 now abandoned, which is a division ofU.S. patent application Ser. No. 10/010,835, filed Dec. 5, 2001, nowU.S. Pat. No. 6,827,456, dated Dec. 7, 2004, which is acontinuation-in-part of U.S. patent application Ser. No. 09/256,275,filed Feb. 23, 1999, now U.S. Pat. No. 6,712,481, dated Mar. 30, 2004,the entire disclosures of which are incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to transreflectors that reflect a greater portionof the light that strikes one side of the transreflectors and transmit agreater portion of the light that strikes the other side of thetransreflectors or vice versa. Also, this invention relates to differentmethods of making transreflectors.

BACKGROUND OF THE INVENTION

A transreflector is an optical device that transmits part of the lightthat strikes it and reflects part of the light that strikes it. Anexample of a transreflector is a beam splitter or half-silvered mirror.Consider the light intensity that strikes a given side of atransreflector, by conservation of energy, the sum of the lightintensity that is (i) transmitted through the transreflector, (ii)reflected by the transreflector and (iii) absorbed by the transreflectormust equal the original intensity striking that side. If one desires toconstruct a transreflector that transmits as much of the light strikingone side of the device as possible while also reflecting as much of thelight striking the opposite side of the device as possible, a beamsplitter type transreflector device is theoretically limited to 50%light transmission and 50% light reflection assuming that the intensityof the light absorbed by the device is zero. Since it is not physicallypossible to create a transreflective device that has zero lightabsorption, a beam splitter type transreflector device that attempts toboth transmit and reflect the maximum amount of light incident on thedevice will be limited to less than 50% transmission and less than 50%reflection.

Transreflectors may be used, for example, with liquid crystal displays(LCDs), used in laptop computers, personal digital assistant devices(PDA), word processors, avionic displays, cell phones and the like topermit the displays to be illuminated in dark environments by abacklight and in lighted environments by ambient light without the needto power the backlight. This is done, for example, by placing thetransreflector between the backlight and the LCD. In lightedenvironments a portion of the ambient light passes through the displayand a portion of this light is then reflected by the transreflector backthrough the LCD to illuminate the display. In dark environments, aportion of the light from the backlight is transmitted through thetransreflector and through the LCD to illuminate the display.

In order to make the display as bright as possible in both lighted anddark environments, the ideal transreflector would transmit 100% of thelight from the backlight striking it from below and reflect 100% of theambient light striking it from above. Optical losses in thetransreflective device, absorption for example, make it impossible toobtain 100% transmittance of light striking the transreflector frombelow and 100% reflection of light striking the transreflector fromabove. However, it is desirable to be as close to 100% transmittance and100% reflection as practically possible.

Beam splitter type transreflectors treat light striking the top surfacefrom above and light striking the bottom surface from below the same,and are limited to less than 50% for both transmission and reflection oflight striking a surface of these devices. Therefore, beam splitter typetransreflective devices are limited to transmitting less than 50% of thelight from the backlight striking them from below and reflecting lessthan 50% of the ambient light striking them from above, which falls farshort of the ideal 100% transmission from below and 100% reflectancefrom above needed to make a display as bright as possible.

In order to make displays as bright as possible, there is a need fortransreflective devices which treat light striking them from abovedifferently than light striking them from below. In addition thesetransreflectors should transmit as much of the light that strikes themfrom below as possible (e.g., greater than 50%), and reflect as much ofthe light that strikes them from above as possible (e.g., greater than50%).

SUMMARY OF THE INVENTION

The present invention relates to transreflectors, transreflector systemsand displays and methods of making transreflectors that reflect more ofthe light that strikes one side of the transreflectors and transmit moreof the light that strikes the opposite side of the transreflectors.

In one form of the invention, the transreflector comprises a transparentsubstrate (which may be a film or plate) having a pattern of opticaldeformities possessing reflective and non-reflective light transmissivesurfaces on or in one side of the substrate. The term “transparent” asused throughout the specification and claims means optically transparentor optically translucent. The transreflector may also comprise two ormore substrate/film layers that have been bonded together with theoptical deformities on outer surfaces of the outermost layers. Theseoptical deformities may comprise grooves or individual opticaldeformities of well defined shape. Also, the size, height, shape,position, angle, density, and/or orientation of the optical deformitiesmay vary across the substrate. The reflective surfaces are coated with areflective coating that may comprise a polarization coating. Thetransmissive surfaces may be textured, lensed or have optical shapes toredirect light, and may also have an optical coating such as anantireflective or polarization coating. The pattern of reflective andnon-reflective light transmissive surfaces may be on the top side of thesubstrate (i.e., the surface nearest the LCD) or the bottom side of thesubstrate (i.e., the surface nearest the backlight). The reflective andtransmissive surfaces may vary in size, shape, angle, density andorientation.

In the case where the pattern of reflective and non-reflective surfacesare on the top side of the transreflector, the other side or bottom ofthe transreflector may either be planar or have optical shapes designedto better transmit a certain distribution of light, for example theoutput distribution of a backlight, and may in addition direct thislight to the light transmissive surfaces. These optical deformities maycomprise grooves or individual optical deformities of well definedshape. Also, the size, height, shape, position, angle, density, and/ororientation of the optical deformities may vary across thetransreflector. An optical coating such as an antireflective orpolarization coating may also be applied to the bottom of thetransreflector in addition to or in place of the optical deformities.

In the case where the pattern of reflective and non-reflective surfacesare on the bottom side of the transreflector, the other side or top ofthe transreflector may either be planar or have optical deformities toredirect light. For example, the top side of the transreflector may haveoptical shapes which redirect light transmitted through thetransreflector more toward the normal direction of the LCD so that morelight from the transreflector is transmitted through the LCD. Theseoptical deformities may comprise grooves including but not limited toprismatic or lenticular grooves, or individual optical deformities ofwell defined shape. Also, the size, shape, angle, density, andorientation of the optical deformities may vary across thetransreflector. The top surface of the transreflector may also betextured or have an optical coating such as an antireflective orpolarization coating.

Such a transreflector may be made by applying a reflective coating toone side of a transparent substrate and then thermoforming such one sideto provide a plurality of spaced angled reflective coated surfaces and aplurality of angled non-coated light transmissive surfaces. The anglesof both the reflective and non-reflective light transmissive surfacesmay be chosen to optimize performance. Also, optical deformities may beformed on the other side of the substrate.

Alternatively, such a transreflector may be made by thermoforming oneside of a transparent substrate to produce a plurality of spaced angledsurfaces and a plurality of other angled surfaces, and then applying areflective coating on the angled surfaces to make them reflectivesurfaces while leaving the other angled surfaces uncoated. This can beaccomplished, for example, by depositing a reflective coating onto theangled surfaces but not onto the other angled surfaces using a line ofsite or other appropriate deposition technique.

In another form of the invention, the transreflector comprises two ormore transparent substrates of different indices of refraction bondedtogether along mating sides of the substrates. The mating side of atleast one of the substrates has a pattern of optical deformities and themating side of the other substrate has an inverse pattern of the opticaldeformities on the mating side of the one substrate. The other side ofthe substrate that has the lower index of refraction may be planar orhave optical deformities designed to accept a specific distribution oflight emitted from a backlight or other light source. The other side ofthe substrate with the higher index of refraction may be textured orhave optical shapes to redirect light entering or exiting thetransreflector from this surface. The other side of either substrate mayalso have an optical coating applied such as an antireflective orpolarization coating. An optical coating may also be applied to eitherof the mating surfaces before the two substrates are bonded together,resulting in an optical film at the mating interface of the twosubstrates after the two substrates are bonded together.

Such a transreflector may be made by preforming a pattern of opticaldeformities on or in one side of the two transparent substrates ofdifferent indices of refraction and using the preformed pattern ofoptical deformities of the one substrate to form an inverse pattern ofthe optical deformities in or on one side of the other substrate bymelting or heat softening one side of the other substrate and pressingthe melted or softened side of the other substrate against the preformedpattern of deformities on or in one side of the one substrate to formthe inverse pattern on or in the one side of the other substrate whilepreventing such one side of the one substrate from melting. Both of thesubstrates are then cooled to cause the one side of the other substrateto solidify and bond with the one side of the one substrate. Also,optical deformities may be formed on or in the other side of either ofthe substrates either before, after or during bonding of the twosubstrates together.

Any of these transreflectors may be used in a transreflector system ordisplay to transmit light emitted by a backlight or other light sourceincident on one side of the transreflectors and for reflecting ambientlight incident on the opposite side of the transreflectors. The side ofthe transreflectors that receives incident light from a backlight orother light source may have optical deformities designed to bettertransmit a particular output distribution of the light emitted from thelight source, and may include an angular shape pattern that changes withthe distance from the input edge of a backlight to compensate forchanges in the angular distribution of the light emitted from thebacklight as the distance from the input edge of the backlightincreases. The optical deformities on the side of the transreflectorsthat receive light from the backlight or other light source may comprisegrooves or individual optical deformities of well defined shape. Also,the size, shape, angle, density, and orientation of the opticaldeformities may vary across the transreflectors.

The other side of the transreflectors which receives incident ambientlight may be textured or have optical shapes to redirect light enteringor exiting the transreflectors from this surface. The optical shapes onthe side of the transreflectors that receive ambient light may comprisegrooves or individual optical deformities of well defined shape. Also,the size, shape, angle, density, and orientation of the opticaldeformities may vary across the transreflectors. An optical coating suchas an antireflective or polarization coating may also be applied toeither surface of the transreflectors in addition to or in place of theoptical deformities.

Likewise, the backlight may have a pattern of individual opticaldeformities for producing a particular light output distribution fromits light emitting surface that have a well defined shape including atleast one sloping surface for reflecting or refracting light impingingon the optical deformities out of the light emitting surface. Thesloping surface of at least some of these deformities may be oriented toface an optically coupled area of the light input edge across thebacklight. Also, at least some of the deformities, which may comprisedepressions in or projections on the light emitting portion of thebacklight/panel member, may vary in size, shape, depth or height,density and/or orientation across the backlight. Moreover, thedeformities may be randomized, staggered, or arranged in a stochasticpattern across the backlight. Further, at least some of the deformitiesmay be arranged in clusters across the backlight, with at least some ofthe deformities in each of the clusters having a different size or shapecharacteristic that collectively produce an average size or shapecharacteristic for each of the clusters that varies across thebacklight. This allows the light output distribution of the backlightand the light input surfaces on the transreflectors that receiveincident light from the backlight to be tuned to each other so that thetransreflectors will better transmit more of the light emitted by thebacklight. Also the side of the backlight closest to the transreflectormay have optical deformities which align with the deformities on or inthe transreflector to increase the efficiency with which light istransmitted from the backlight to the transreflector. The region betweenthe aligned backlight and transreflector deformities may contain arefraction index matching material to further increase efficiency. Adisplay may be placed in close proximity to the side of thetransreflectors facing away from the backlight.

To the accomplishment of the foregoing and related ends, the invention,then, comprises the features hereinafter more fully described andparticularly pointed out in the claims, the following description andannexed drawings setting forth in detail certain illustrativeembodiments of the invention, these being indicative, however, of butseveral of the various ways in which the principles of the invention maybe employed.

BRIEF DESCRIPTION OF THE DRAWINGS

In the annexed drawings:

FIG. 1 a is a schematic side elevation view of one form oftransreflector system in accordance with the present invention;

FIGS. 1 b-1 d are schematic side elevation views of different variationsof the transreflector system shown in FIG. 1 a;

FIGS. 2 and 3 a are schematic side elevation views of other forms oftransreflector systems in accordance with the present invention;

FIGS. 3 b-3 d are schematic side elevation views of different variationsof the transreflector system shown in FIG. 3 a;

FIGS. 4 a-4 c are schematic perspective views of a transreflector of thetype shown in FIG. 1 a in which the optical deformities on one side ofthe transreflector are comprised of grooves;

FIGS. 5 a-5 d are schematic perspective views of a transreflector of thetype shown in FIG. 1 a in which the optical deformities on one side ofthe transreflector are individual optical deformities each having a welldefined shape;

FIGS. 6 a-6 e are schematic perspective views of other geometric shapesthat the individual optical deformities of FIGS. 5 a-5 d may take;

FIGS. 7 a-7 g are schematic perspective views of different patterns ofoptical deformities on or in one or more other surfaces of thetransreflectors of FIGS. 1 a, 2 and 3 a;

FIGS. 8 a-8 i are schematic perspective views of different geometricshapes of individual optical deformities that can be substituted for theoptical deformities shown in FIGS. 7 c-e;

FIGS. 9 a-9 c are schematic illustrations of one method of making thelight reflective and transmissive surfaces of the transreflectors shownin FIGS. 1 a and 2;

FIGS. 10 a-10 c are schematic illustrations of another method of makingthe light reflective and transmissive surfaces of the transreflectorsshown in FIGS. 1 a and 2;

FIG. 11 is a schematic illustration of one method of making thetransreflector shown in FIG. 3 a;

FIGS. 12 and 13 are enlarged schematic fragmentary plan views of asurface area of a backlight/light emitting panel assembly showingvarious forms of optical deformities in accordance with this inventionformed on or in a surface of the backlight;

FIGS. 14 and 15 are enlarged longitudinal sections through one of theoptical deformities of FIGS. 12 and 13, respectively;

FIGS. 16 and 17 are enlarged schematic longitudinal sections throughother forms of optical deformities in accordance with this inventionformed on or in a surface of a backlight;

FIGS. 18-26 are enlarged schematic perspective views of backlightsurface areas containing various patterns of individual opticaldeformities of other well defined shapes in accordance with thisinvention;

FIG. 27 is an enlarged schematic longitudinal section through anotherform of optical deformity in accordance with this invention formed on orin a surface of a backlight;

FIGS. 28 and 29 are enlarged schematic top plan views of backlightsurface areas containing optical deformities similar in shape to thoseshown in FIGS. 24 and 25 arranged in a plurality of straight rows alongthe length and width of the surface areas;

FIGS. 30 and 31 are enlarged schematic top plan views of backlightsurface areas containing optical deformities also similar in shape tothose shown in FIGS. 24 and 25 arranged in staggered rows along thelength of the surface areas;

FIGS. 32 and 33 are enlarged schematic top plan views of backlightsurface areas containing a random or variable pattern of clusters ofdifferent sized optical deformities on the surface areas;

FIG. 34 is an enlarged schematic perspective view of a backlight surfacearea showing optical deformities in accordance with this inventionincreasing in size as the distance of the deformities from the lightinput surface increases or intensity of the light increases along thelength of the surface area;

FIGS. 35 and 36 are schematic perspective views showing differentangular orientations of the optical deformities along the length andwidth of a backlight surface area; and

FIGS. 37 and 38 are enlarged perspective views schematically showing howexemplary light rays emitted from a focused light source are reflectedor refracted by different individual optical deformities of well definedshapes of a backlight surface area in accordance with this invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now in detail to the drawings, and initially to FIGS. 1 a, 2and 3 a, these figures schematically show three different transreflectorsystems 1, 2 and 3 in accordance with this invention each including atransreflector 4, 5 and 6 placed between a display D such as a liquidcrystal display or membrane switch and a backlight BL for reflectingmore of the ambient light that passes through the display back out thedisplay making it more visible (e.g., brighter) in a lightedenvironment, and for transmitting more of the light from the backlightthrough the transreflector and out the display to illuminate the displayin a dark environment.

Each of the transreflectors 4, 5 shown in FIGS. 1 a and 2 comprises atransparent (i.e., optically transparent or translucent) substrate 7which may be a plate or film including a multilayer film comprising forexample a carrier film and an ultra-violet curable layer. On or in oneside of the substrate are a plurality of spaced optical elements ordeformities 8 each including one or more light reflective surfaces 9 anda non-reflective light transmissive surface 10. The deformities 8 mayeither be grooves 11 as schematically shown in FIGS. 4 a-c or a patternof individual optical deformities 12 each having a well defined shape asschematically shown in FIGS. 5 a-d. The grooves 11 may be of the sameheight throughout their length as schematically shown in FIGS. 4 a and 4b or may vary in height along their length as schematically shown inFIG. 4 c. Also the variation in height may be different from one groove11 to another as further schematically shown in FIG. 4 c. Each of theindividual optical deformities 12 may be of substantially the same sizeand shape as schematically shown in FIGS. 5 a and 5 b or of differentsizes and geometric shapes as schematically shown in FIG. 5 c. Theoptical deformities 12 shown in FIG. 5 a each have only two surfaces, aplanar reflective surface 9 and a curved light transmissive surface 10,whereas the optical deformities 12 shown in FIG. 5 b each have apyramidal shape including a plurality of reflective surfaces 9 and onelight transmissive surface 10.

Also each of the optical deformities 12 may be arranged in a patternwith the light transmissive surface 10 of each of the deformities facingthe same general direction as schematically shown in FIGS. 1 a and 5 a-5c for receiving light from a backlight lit by a single light source 50optically coupled to one input edge only as schematically shown in FIG.1 a or arranged in a pattern with the light transmissive surfaces 10 andlight reflective surfaces 9 of different optical deformities 12generally facing in opposite directions as schematically shown in FIGS.1 b and 5 d for receiving light from a backlight lit by two lightsources 50 optically coupled to two input edges as schematically shownin FIG. 1 b.

In FIG. 5 a the reflective surface 9 of the individual opticaldeformities 12 is rounded or curved and the light transmissive surface10 is planar. However, it will be appreciated that the reflectivesurface 9 of the individual optical deformities 12 may be planar and thelight transmissive surface 10 rounded as schematically shown in FIG. 6a. Alternatively, both the reflective surface(s) 9 and lighttransmissive surface 10 of the individual optical deformities 12 may beplanar as schematically shown in FIGS. 6 b-6 e. Also, the reflectivesurface(s) 9 and light transmissive surface 10 of the individual opticaldeformities 12 may intersect each other as schematically shown in FIGS.5 a-5 d and 6 a, 6 b and 6 d or may be spaced from each other by anintermediate surface 13 extending parallel to the general plane of thetransreflectors as schematically shown in FIG. 6 c or intersecting thegeneral plane of the transreflectors as schematically shown in FIG. 6 e.Moreover, the individual optical deformities may have rounded or curvedends 14 as schematically shown in FIGS. 6 b and 6 c.

The light transmissive surfaces 10 are angled to transmit a greaterportion of the light from the backlight and direct the light through thetransreflector and out through the other side of the transreflector.Also the projected area of the light transmissive surfaces 10 onto aplane normal to the maximum output angle of the light rays R emittedfrom the backlight BL is substantially less than the projected area ofthe reflective surfaces 9 onto the general plane of the transreflectors4, 5. This enables the reflective surfaces 9 to reflect more of theambient light passing through the display D back through the display asschematically shown in FIGS. 1 a and 2 making the display more visible(e.g., brighter) in a lighted environment. At the same time, the lighttransmissive surfaces 10 will transmit more of the light incident on thetransreflectors 4, 5 from a backlight BL or other light source out thedisplay to illuminate the display in a dark environment.

The reflective surfaces 9 are coated with a suitable reflective coating15 such as a metallized coating which may also comprise a polarizationcoating, whereas the light transmissive surfaces 10 may be textured orlensed as schematically shown for example at 16 in FIGS. 1 a and 2 toredirect the light passing through the light transmissive surfaces.

In the embodiment shown in FIG. 1 a, the side of the transreflector 4furthest from the display D includes the reflective surfaces 9 andassociated light transmissive surfaces 10, whereas in the embodimentshown in FIG. 2, the side of the transreflector 5 closest to the displayD includes the reflective surfaces 9 and associated light transmissivesurfaces 10. In either case, a greater portion of the ambient light thatpasses through the display will be reflected by the reflective surfaces9 back through the display making it more visible in a lightedenvironment.

In a dark environment, in the case of the transreflector 4 shown in FIG.1 a, the light transmissive surfaces 10 between the reflective surfaces9 on the side of the transreflector closest to the backlight BL areangled to transmit a greater portion of the light from the backlight anddirect the light through the transreflector and out through the otherside of the transreflector. The other side of the transreflector 4 maybe planar as shown in phantom lines 17 in FIG. 1 a and in solid lines inFIGS. 1 c and 4 b, or have a texture, chemical etch or laser etch orhave optical deformities 18 in or on the other side of thetransreflector as shown in solid lines in FIGS. 1 a, 1 b, 1 d, 4 a and 4c to redirect the light more toward the normal direction of the displayD to better illuminate the display in a dark environment. The other sidemay also have an optical film (coating, layer) such as an antireflectionor polarization recycling film 17′ (shown in phantom lines in FIG. 1 aand in solid lines in FIG. 4 b and only on the right hand side of FIG. 1c for purposes of comparison). The light that is emitted from thebacklight BL is unpolarized (i.e., made up of two polarizations P₁ andP₂ as schematically shown in FIG. 1 c. When this unpolarized light hitsthe polarization recycling coating 17′, polarization P₁ is transmittedand polarization P₂ is reflected. Polarization P₁ continues and istransmitted through the LCD. Polarization P₂ is reflected back into thetransreflector where it reflects and is scattered back toward thereflective polarizer 17′, once again becoming a mixture of bothpolarizations P₁ and P₂ and the process repeats.

If the reflective polarization film 17′ is not present as shown forcomparison of function on the left hand side of the transreflector inFIG. 1 c, the unpolarized light P₁ and P₂ that leaves the backlight BLand is transmitted by the transreflector strikes the LCD andpolarization P₁ is transmitted by the LCD while polarization P₂ isabsorbed resulting in a loss of substantially 50% of the light.

In the case of the transreflector 5 shown in FIG. 2, the other side ofthe transreflector may either be planar as shown by phantom lines 17 inFIG. 2, or have a texture, chemical etch or laser etch or opticaldeformities 19 as shown in solid lines in FIG. 2 including surfaces 20angled to transmit light from the backlight or other light source anddirect the light to the light transmissive surfaces 10 in the side ofthe transreflector closest to the display D for increasing the amount oflight transmitted from the backlight through the transreflector toilluminate the display. The other side may also have an optical coating17′ such as an antireflection or polarization coating. These opticaldeformities 18, 19 can either be grooves or individual deformities eachhaving a well defined shape as described hereafter.

The optical deformities 18 in or on the top side of the transreflector 4shown in FIG. 1 a and the optical deformities 19 in or on the bottomside of the transreflector 5 shown in FIG. 2 may consist of prismatic orlenticular grooves 21, 22 of the type schematically shown, for example,in FIGS. 7 a and b or two sets of grooves 21 or 22 cut perpendicular toeach other (e.g., cross grooves) resulting in a pyramid structure 30 asschematically shown in FIG. 7 c. Alternatively, such optical deformities18, 19 may consist of a pattern of individual optical deformities eachhaving a well defined shape that may be in a close array 23 as shown inFIG. 7 d or in a spaced array 24 as shown in FIG. 7 e, and may either bein rows 25 as shown in FIGS. 7 d and e or randomized as shown at 26 inFIG. 7 f. Moreover, the pattern of individual optical deformities 18, 19may randomly overlap each other with the optical deformities eitherbeing staggered with respect to each other or intersecting orinterlocking each other as schematically shown in FIG. 7 g. Also, theposition, size, height, density, angle, orientation and/or shape of theoptical deformities may vary across the substrate.

The individual optical deformities 18, 19 may also take many differentshapes including, for example, a pyramid 30 with triangular shape sides31 as shown in FIG. 8 a, a frusto-pyramid 32 with trapezoidal shapesides 33 and a planar top 34 as shown in FIG. 8 b, a relatively steepplanar angled surface 35 with long rounded or curved sides 36 as shownin FIG. 8 c, a conical shape 37 as shown in FIG. 8 d, a frusto-conicalshape 38 with a planar top 39 as shown in FIG. 8 e, a relatively shallowsloping planar surface 40 with steeper rounded or curved sides 41 asshown in FIG. 8 f, a pair of intersecting oppositely sloping sides 42with oppositely rounded or curved ends 43 as shown in FIG. 8 g, a pairof oppositely sloping planar sides 44 with oppositely rounded or curvedends 45 and a planar top 46 as shown in FIG. 8 h, and a semisphericalshape 47 as shown in FIG. 8 i. Moreover, more than one type of shape ofoptical deformities 18, 19 may be provided in or on one or both sides ofthe transreflector.

In any case, the patterns of the position, angle, density, size, height,shape and orientation of the deformities on the side of thetransreflectors 4, 5 closest to the backlight are designed to transmit aspecific light distribution from the backlight. To that end, the anglesof the surfaces 10 of transreflector 4 and surfaces 20 of transreflector5 may be varied as the distance from the light source 50 increases toaccount for the way the backlight BL emits light differently as thedistance from the light source increases.

FIGS. 9 and 10 show two different methods of making the light reflectiveand light transmissive surfaces 9 and 10 of the transreflectors 4 and 5shown in FIGS. 1 a and 2. In the method shown in FIG. 9, a reflectivefilm, layer or coating 15 may be applied to one side of a transparentsubstrate 7 which may be comprised of one or more layers each having aconstant index of refraction (see FIG. 9 a). Then the reflective coatingmay be removed from selected surfaces or areas as by thermoforming thecoated side of the transparent substrate using a press or roller 51 toform a plurality of spaced angled or sloping reflective coated surfacesor areas 9 separated by a plurality of spaced other angled or slopingnoncoated light transmissive surfaces or areas 10 as shown in FIGS. 9 band 9 c. During or after the thermoforming process, the lighttransmissive surfaces 10 may be textured or lensed for redirecting lightpassing through the light transmissive surfaces as desired. The otherside of the substrate 7 may be left planar as shown in solid lines 17 inFIG. 9 b and phantom lines 17 in FIG. 9 c or textured or provided withoptical deformities 18 as shown in solid lines in FIG. 9 c. Also anoptical coating 17′ may be applied to the other side as further shown inphantom lines in FIG. 9 c.

The method shown in FIG. 10 differs from that shown in FIG. 9 in that noreflective coating is applied to the transparent substrate 7 until afterone side of the substrate is thermoformed to produce a plurality ofspaced angled or sloping surfaces 9 separated by a plurality of otherangled or sloping surfaces 10 as shown in FIG. 10 b. Then a reflectivecoating 15 is applied only on the angled surfaces 9 as shown in FIG. 10c using for example a line of site deposition technique to form thereflective surfaces 9 while leaving the light transmissive surfaces 10uncoated. Alternatively, the reflective coating 15 may be hot stampedonto the reflective surfaces 9.

The transreflector 6 shown in FIG. 3 differs from those shown in FIGS. 1a and 2 in that it comprises at least two transparent substrates 55, 56of different indices of refraction bonded together, with opticaldeformities 57, 58 at the interface 59 between the two substrates. Thesubstrates 55, 56 may be completely or partially bonded together orbonded together in selected areas as desired. The substrate 55 closestto the display D has a higher index of refraction than the substrate 56furthest from the display. The mating side of one of the substrates (forexample substrate 55) includes a pattern of optical deformities 57 andthe mating side of the other substrate 56 includes an inverse pattern ofoptical deformities 58. These optical deformities may comprise groovesof different shapes including for example prismatic grooves havingplanar sides with sharp or curved peaks and valleys as shown in FIGS. 3a and 3 b, respectively, or curved sides as shown in FIG. 3 c orlenticular grooves or cross grooves or individual optical deformitieseach having a well defined shape as previously described andschematically illustrated in FIGS. 7 and 8 such that the difference inthe indices of refraction of the two substrates causes a greater portionof the ambient light that passes through the display and enters thehigher index side 55 of the transreflector 6 to be totally internallyreflected at both the interior high/low interface 59 between the twosubstrates and at the bottom low/air interface 60 to make the displaymore visible in a lighted environment.

Light rays R from the backlight BL enter through the lower index side 56of the transreflector 6 and are transmitted through the transreflectorto the display D. The side 17 of the lower index substrate 56 closest tothe backlight BL may be either planar as shown in phantom lines in FIG.3 a, textured or have a pattern of optical deformities 61 as shown insolid lines in FIG. 3 a which may be similar to the optical deformities19 of the transreflector 5 shown in FIG. 2 to optimize the ability ofthe transreflector 6 to transmit the specific distribution of light thatis emitted from the backlight BL by designing the angle, density, size,shape and orientation of the optical deformities to transmit thespecific light distribution emitted from the backlight in the mannerpreviously described. Also, the angles of the light entrance surfaces 62of the optical deformities 61 of the transreflector 6 may be made tovary as the distance from the light source 50 increases as schematicallyshown in FIG. 3 a to account for the way that the backlight emits lightdifferently as the distance from the light source increases, similar tothe light entrance surfaces 10 and 20 of the transreflectors 4 and 5shown in FIGS. 1 a and 2.

If desired, the interface 59 between the two substrates 55, 56 of thetransreflector 6 may be provided with an anti-reflective, metallizedand/or polarization coating 63 as schematically shown in FIG. 3 a. Also,a diffuser or brightness enhancement film or optical deformities or atexture 64 may be applied to the outer surface of the higher indexsubstrate 55 to obtain a desired light output distribution from thetransreflector 6. Further, the transreflector 6 may comprise more thantwo transparent substrates 55, 56, 56 a of different indices ofrefraction bonded together along mating sides of the substrates withoptical deformities on or in the outer surfaces of the outermost layers55, 56 a as schematically shown in FIG. 3 d.

One method of making the transreflector 6 shown in FIG. 3 a is topreform the desired pattern of optical deformities 57 in or on one sideof one of the substrates (in this case substrate 55) and use thepreformed pattern of optical deformities 57 to form an inverse patternof the optical deformities 58 in or on one side of the other substrate56 and then bond the two substrates together with the opticaldeformities 57 and inverse optical deformities 58 in mating engagementwith each other as schematically shown in FIG. 11. The inverse patternof optical deformities 58 may be formed in or on one side of the othersubstrate 56 by passing the other substrate 56 between a series ofpreheaters 65 to melt or heat soften the other substrate 56 and thenpressing the melted or heat softened substrate 56 against the onesubstrate 55 using a hot roller 66 which brings the substrate 56 to beformed to its final temperature while preventing the one substrate 55from melting by passing the one substrate 55 through a cold roller 67 asshown in FIG. 11. Then both substrates 55, 56 may be passed through apair of cold rollers 68, 69 to cause the melted and/or heat softenedsubstrate 56 to solidify and bond with the preformed substrate 55 asfurther shown in FIG. 11.

Alternatively, a transparent ultra-violet curable polymer 56 having anindex of refraction less than the index of refraction of the substrate55 may be used in place of the other substrate. The uncured polymer 56is applied to the preformed pattern of optical deformities 57 in or onone side of the one substrate 55 and then cured to form an inversepattern of the optical deformities 58 in or on the polymer and bond thepolymer to the one side of the one substrate.

The backlight BL may be substantially flat, or curved, or may be asingle layer or multi-layers, and may have different thicknesses andshapes as desired. Moreover, the backlight may be flexible or rigid, andbe made of a variety of compounds. Further, the backlight may be hollow,filled with liquid, air, or be solid, and may have holes or ridges.

Also, the light source 50 may be of any suitable type including, forexample, an arc lamp, an incandescent bulb which may also be colored,filtered or painted, a lens end bulb, a line light, a halogen lamp, alight emitting diode (LED), a chip from an LED, a neon bulb, a coldcathode fluorescent lamp, a fiber optic light pipe transmitting from aremote source, a laser or laser diode, or any other suitable lightsource. Additionally, the light source 50 may be a multiple colored LED,or a combination of multiple colored radiation sources in order toprovide a desired colored or white light output distribution. Forexample, a plurality of colored lights such as LEDs of different colors(e.g., red, blue, green) or a single LED with multiple color chips maybe employed to create white light or any other colored light outputdistribution by varying the intensities of each individual coloredlight.

A pattern of optical deformities may be provided on one or both sides ofthe backlight BL or on one or more selected areas on one or both sidesof the backlight as desired. As used herein, the term opticaldeformities means any change in the shape or geometry of a surfaceand/or coating or surface treatment that causes a portion of the lightto be emitted. These deformities can be produced in a variety ofmanners, for example, by providing a painted pattern, an etched pattern,machined pattern, a printed pattern, a hot stamp pattern, or a moldedpattern or the like on selected areas of the backlight. An ink or printpattern may be applied for example by pad printing, silk printing,inkjet, heat transfer film process or the like. The deformities may alsobe printed on a sheet or film which is used to apply the deformities tothe backlight. This sheet or film may become a permanent part of thebacklight for example by attaching or otherwise positioning the sheet orfilm against one or both sides of the backlight in order to produce adesired effect.

By varying the density, opaqueness or translucence, shape, depth, color,area, index of refraction or type of deformities on or in an area orareas of the backlight, the light output of the backlight can becontrolled. The deformities may be used to control the percent of lightoutput from a light emitting area of the backlight. For example, lessand/or smaller size deformities may be placed on surface areas whereless light output is wanted. Conversely, a greater percentage of and/orlarger deformities may be placed on surface areas of the backlight wheregreater light output is desired.

Varying the percentages and/or size of deformities in different areas ofthe backlight is necessary in order to provide a substantially uniformlight output distribution. For example, the amount of light travelingthrough the backlight will ordinarily be greater in areas closer to thelight source than in other areas further removed from the light source.A pattern of deformities may be used to adjust for the light varianceswithin the backlight, for example, by providing a denser concentrationof deformities with increased distance from the light source therebyresulting in a more uniform light output distribution from thebacklight.

The deformities may also be used to control the output ray angledistribution from the backlight to suit a particular application. Forexample, if the backlight is used to backlight a liquid crystal display,the light output will be more efficient if the deformities cause thelight rays to emit from the backlight at predetermined ray angles suchthat they will pass through the liquid crystal display with low loss.Additionally, the pattern of optical deformities may be used to adjustfor light output variances attributed to light extractions of thebacklight. The pattern of optical deformities may be printed on thebacklight surface areas utilizing a wide spectrum of paints, inks,coatings, epoxies or the like, ranging from glossy to opaque or both,and may employ half-tone separation techniques to vary the deformitycoverage. Moreover, the pattern of optical deformities may be multiplelayers or vary in index of refraction.

Print patterns of optical deformities may vary in shapes such as dots,squares, diamonds, ellipses, stars, random shapes, and the like. Also,print patterns of sixty lines per inch or finer are desirably employed.This makes the deformities or shapes in the print patterns nearlyinvisible to the human eye in a particular application, therebyeliminating the detection of gradient or banding lines that are commonto light extracting patterns utilizing larger elements. Additionally,the deformities may vary in shape and/or size along the length and/orwidth of the backlight. Also, a random placement pattern of thedeformities may be utilized throughout the length and/or width of thebacklight. The deformities may have shapes or a pattern with no specificangles to reduce moiré or other interference effects. Examples ofmethods to create these random patterns are printing a pattern of shapesusing stochastic print pattern techniques, frequency modulated half tonepatterns, or random dot half tones. Moreover, the deformities may becolored in order to effect color correction in the backlight. The colorof the deformities may also vary throughout the backlight, for example,to provide different colors for the same or different light outputareas.

In addition to or in lieu of the patterns of optical deformities, otheroptical deformities including prismatic or lenticular grooves or crossgrooves such as shown in FIGS. 7 a-c, or depressions or raised surfacesof various shapes using more complex shapes in a mold pattern may bemolded, etched, stamped, thermoformed, hot stamped or the like into oron one or more surface areas of the backlight. The prismatic orlenticular surfaces, depressions or raised surfaces will cause a portionof the light rays contacted thereby to be emitted from the backlight.Also, the angles of the prisms, depressions or other surfaces may bevaried to direct the light in different directions to produce a desiredlight output distribution or effect. Moreover, the reflective orrefractive surfaces may have shapes or a pattern with no specific anglesto reduce moiré or other interference effects.

A back reflector 75 may be attached or positioned against one side ofthe backlight BL as schematically shown in FIGS. 1 a, 2 and 3 a in orderto improve light output efficiency of the backlight by reflecting thelight emitted from that side back through the panel for emission throughthe opposite side. Additionally, a pattern of optical deformities 76 maybe provided on one or both sides of the backlight as schematically shownin FIGS. 1 a, 2 and 3 a in order to change the path of the light so thatthe internal critical angle is exceeded and a portion of the light isemitted from one or both sides of the backlight. These opticaldeformities 76 in the backlight BL may have the inverse shape of theoptical deformities 8 of the transreflector 4 and be aligned (and ifdesired overlap each other) as schematically shown in FIG. 1 d toincrease the efficiency of light transfer from the backlight to thetransreflector. Further, the region between the aligned backlight andtransreflector deformities 76 and 8 may contain a refraction indexmatching material 79 to further increase the efficiency of such lighttransfer. Moreover, a transparent film, sheet or plate 77 may beattached or positioned against the side or sides of the backlight fromwhich light is emitted as schematically shown in FIGS. 1 a and 2 tofurther improve the uniformity of the light output distribution. Forexample, the film, sheet or plate may be a brightness enhancement filmor a diffuser.

FIGS. 12-15 show other optical deformities 80 which may either beindividual projections 81 on the respective backlight surface areas 82or individual depressions 83 in such surface areas. In either case, eachof these optical deformities 80 has a well defined shape including areflective or refractive surface 84 that intersects the respectivebacklight surface area 82 at one edge 85 and has a uniform slopethroughout its length for more precisely controlling the emission oflight by each of the deformities. Along a peripheral edge portion 86 ofeach reflective/refractive surface 84 is an end wall 87 of eachdeformity 80 that intersects the respective panel surface area 82 at agreater included angle I than the included angle I′ between thereflective/refractive surfaces 84 and the panel surface area 82 (seeFIGS. 14 and 15) to minimize the projected surface area of the end wallson the panel surface area. This allows more deformities 80 to be placedon or in the panel surface areas than would otherwise be possible if theprojected surface areas of the end walls 87 were substantially the sameas or greater than the projected surface areas of thereflective/refractive surfaces 84.

In FIGS. 12 and 13 the peripheral edge portions 86 of thereflective/refractive surfaces 84 and associated end walls 87 are curvedin the transverse direction. Also in FIGS. 14 and 15 the end walls 87 ofthe deformities 80 are shown extending substantially perpendicular tothe reflective/refractive surfaces 84 of the deformities. Alternatively,such end walls 84 may extend substantially perpendicular to the panelsurface areas 82 as schematically shown in FIGS. 16 and 17. Thisvirtually eliminates any projected surface area of the end walls 87 onthe panel surface areas 82 whereby the density of the deformities on thepanel surface areas may be even further increased.

The optical deformities may also be of other well defined shapes toobtain a desired light output distribution from a panel surface area.FIG. 18 shows individual light extracting deformities 88 on a panelsurface area 82 each including a generally planar, rectangularreflective/refractive surface 89 and associated end wall 90 of a uniformslope throughout their length and width and generally planar side walls91. Alternatively, the deformities 88′ may have rounded or curved sidewalls 92 as schematically shown in FIG. 19.

FIG. 20 shows individual light extracting deformities 93 on a panelsurface area 82 each including a planar, sloping triangular shapedreflective/refractive surface 94 and associated planar, generallytriangularly shaped side walls or end walls 95. FIG. 21 shows individuallight extracting deformities 96 each including a planar slopingreflective/refractive surface 97 having angled peripheral edge portions98 and associated angled end and side walls 99 and 100.

FIG. 22 shows individual light extracting deformities 101 which aregenerally conically shaped, whereas FIG. 23 shows individual lightextracting deformities 102 each including a roundedreflective/refractive surface 103 and rounded end walls 104 and roundedor curved side walls 105 all blended together. These additional surfaceswill reflect or refract other light rays impinging thereon in differentdirections to spread light across the backlight/panel member BL toprovide a more uniform distribution of light emitted from the panelmember.

Regardless of the particular shape of the reflective/refractive surfacesand end and side walls of the individual deformities, such deformitiesmay also include planar surfaces intersecting the reflective/refractivesurfaces and end and/or side walls in parallel spaced relation to thepanel surface areas 82. FIGS. 24-26 show deformities 106, 107 and 108 inthe form of individual projections on a panel surface area havingrepresentative shapes similar to those shown in FIGS. 18, 19 and 22,respectively, except that each deformity is intersected by a planarsurface 109 in parallel spaced relation to the panel surface area 82. Inlike manner, FIG. 27 shows one of a multitude of deformities 110 in theform of individual depressions 111 in a panel surface area 82 eachintersected by a planar surface 109 in parallel spaced relation to thegeneral planar surface of the panel surface area 82. Any light rays thatimpinge on such planar surfaces 109 at internal angles less than thecritical angle for emission of light from the panel surface area 82 willbe internally reflected by the planar surfaces 109, whereas any lightrays impinging on such planar surfaces 109 at internal angles greaterthan the critical angle will be emitted by the planar surfaces withminimal optical discontinuities, as schematically shown in FIG. 27.

Where the deformities are projections on the panel surface area 82, thereflective/refractive surfaces extend at an angle away from the panel ina direction generally opposite to that in which the light rays from thelight source 50 travel through the panel as schematically shown in FIGS.14 and 16. Where the deformities are depressions in the panel surfacearea, the reflective/refractive surfaces extend at an angle into thepanel in the same general direction in which the light rays from thelight source 50 travel through the panel member as schematically shownin FIGS. 15 and 17.

Regardless of whether the deformities are projections or depressions onor in the panel surface areas 82, the slopes of the lightreflective/refractive surfaces of the deformities may be varied to causethe light rays impinging thereon to be either refracted out of the lightemitting panel or reflected back through the panel and emitted out theopposite side of the panel which may be etched to diffuse the lightemitted therefrom or covered by a transparent film to produce a desiredeffect. Also, the pattern of optical deformities on the panel surfacearea may be uniform or variable as desired to obtain a desired lightoutput distribution from the panel surface areas. FIGS. 28 and 29 showdeformities 106 and 107 similar in shape to those shown in FIGS. 24 and25 arranged in a plurality of generally straight uniformly spaced apartrows along the length and width of a panel surface area 82, whereasFIGS. 30 and 31 show such deformities 106 and 107 arranged in staggeredrows that overlap each other along the length of a panel surface area.

Also, the size, including the width, length and depth or height as wellas the angular orientation and position of the optical deformities mayvary along the length and/or width of any given panel surface area toobtain a desired light output distribution from the panel surface area.FIGS. 32 and 33 show a random or variable pattern of different sizedeformities 88 and 88′ similar in shape to those shown in FIGS. 18 and19, respectively, arranged in staggered rows on a panel surface area 82,whereas FIG. 34 shows deformities 107 similar in shape to those shown inFIG. 25 increasing in size as the distance of the deformities from thelight source increases or intensity of the light decreases along thelength and/or width of the panel surface area. The deformities 88 and88′ are shown in FIGS. 32 and 33 arranged in clusters across the panelsurface, with at least some of the deformities in each cluster having adifferent size or shape characteristic that collectively produce anaverage size or shape characteristic for each of the clusters thatvaries across the panel surface. For example, at least some of thedeformities in each of the clusters may have a different depth or heightor different slope or orientation that collectively produce an averagedepth or height characteristic or average slope or orientation of thesloping surface that varies across the panel surface. Likewise at leastsome of the deformities in each of the clusters may have a differentwidth or length that collectively produce an average width or lengthcharacteristic that varies across the panel surface. This allows one toobtain a desired size or shape characteristic beyond machinerytolerances, and also defeats moiré and interference effects.

FIGS. 35 and 36 schematically show different angular orientations ofoptical deformities 115 of any desired shape along the length and widthof a panel surface area 82. In FIG. 35 the deformities are arranged instraight rows 116 along the length of the panel surface area but thedeformities in each of the rows are oriented to face the light source 50so that all of the deformities are substantially in line with the lightrays being emitted from the light source. In FIG. 36 the deformities 115are also oriented to face the light source 50 similar to FIG. 35. Inaddition, the rows 117 of deformities in FIG. 36 are in substantialradial alignment with the light source 50.

FIGS. 37 and 38 schematically show how exemplary light rays 120 emittedfrom a focused light source 50 insert molded or cast within a lighttransition area 121 of a light emitting panel assembly BL in accordancewith this invention are reflected during their travel through the lightemitting panel member 122 until they impinge upon individual lightextracting deformities 80, 107 of well defined shapes on or in a panelsurface area 82 causing more of the light rays to be reflected orrefracted out of one side 123 of the panel member than the other side124. In FIG. 37 the exemplary light rays 120 are shown being reflectedby the reflective/refractive surfaces 84 of the deformities 80 in thesame general direction out through the same side 123 of the panelmember, whereas in FIG. 38 the light rays 120 are shown being scatteredin different directions within the panel member 122 by the rounded sidewalls 92 of the deformities 107 before the light rays arereflected/refracted out of the same side 123 of the panel member. Such apattern of individual light extracting deformities of well definedshapes in accordance with the present invention can cause 60 to 70% ormore of the light received through the input edge 125 of the panelmember to be emitted from the same side of the panel member.

From the foregoing, it will be apparent that the light outputdistribution of the backlights of the present invention and the lightinput surfaces of the transreflectors of the present invention thatreceive incident light from the backlights may be tuned to each other sothat the transreflectors will better transmit more of the light emittedby the backlights through the transreflectors.

Although the invention has been shown and described with respect tocertain embodiments, it is obvious that equivalent alterations andmodifications will occur to others skilled in the art upon the readingand understanding of the specification. In particular, with regard tothe various functions performed by the above described components, theterms (including any reference to a “means”) used to describe suchcomponents are intended to correspond, unless otherwise indicated, toany component which performs the specified function of the describedcomponent (e.g., that is functionally equivalent), even though notstructurally equivalent to the disclosed component which performs thefunction in the herein illustrated exemplary embodiments of theinvention. In addition, while a particular feature of the invention mayhave been disclosed with respect to only one embodiment, such featuremay be combined with one or more other features of other embodiments asmay be desired and advantageous for any given or particular application.

1. A method of making an optical film, plate or substrate out of atleast two transparent substrates having different indices of refractioncomprising the steps of preforming a pattern of optical deformities onor in one side of one of the substrates, melting or heat softening oneside of an other substrate and pressing the melted or softened side ofthe other substrate in direct contact against the preformed pattern ofoptical deformities on or in the one side of the one substrate to formthe inverse pattern of optical deformities in or on the melted orsoftened side of the other substrate, and then cooling the substrates tocause the one side of the other substrate to harden and bond in directcontact to the one side of the one substrate with the opticaldeformities and inverse optical deformities in direct mating engagementwith one another.
 2. The method of claim 1 wherein the film, plate orsubstrate includes more than two layers with interfaces between thelayers, and there are optical deformities formed on at least one of theinterfaces between the layers.
 3. The method of claim 1 wherein thefilm, plate or substrate is edge lit by a light source and emits lightfrom at least one surface of the film, plate or substrate.
 4. The methodof claim 1 further comprising the step of forming optical deformities inthe other side of the substrate that has the lower index of refractionshaped to transmit a specific distribution of light emitted from abacklight or other light source.
 5. The method of claim 1 furthercomprising the step of forming optical deformities in the other side ofthe substrate that has the higher index of refraction shaped to redirectlight.
 6. The method of claim 1 further comprising the step of applyinga texture to the other side of the substrate that has the higher indexof refraction.